1. Field of the Invention
The invention relates generally to surgical instruments and procedures and more particularly to apparatus and a procedure for verifying proper femoral intramedullary channel preparation and seating therein of a prosthetic femoral hip implant.
2. Prior Art
In a hip replacement surgical procedure where the head and neck of the posterior femur are removed and replaced with a prosthetic implant it is required that, once installed, this prosthetic device remain stationary for proper healing and prosthesis functioning. In practice, if a prosthetic implant is loose such that rotational micromovement of the implant within the bone will occur, particularly for a prosthesis that is secured by means of friction or porous ingrowth coatings, that rotational movement will loosen the fit, shearing away the ingrowth, and prohibiting healing.
Accordingly, the present invention is directed to a procedure and apparatus for verifying mechanical fixation of a prosthetic femoral implant during a hip joint replacement surgical procedure.
The present invention involves a system and apparatus for torsionally testing a prosthetic hip implant to verify proper seating. In this procedure, proper seating is assumed where it is determined the implant will maintain stability when subjected to application of a certain torsional force in inch points, as has been determined experimentally. While torsional testing apparatus and procedure have heretofore been practiced in other surgical disciplines, such have not involved prosthetic hip implants. For example, a patent to Boland, U.S. Pat. No. 4,576,158, shows a torsional testing device for testing bone stability; with a patent to Cordey, U.S. Pat. No. 4,359,906, showing a device for tightening a screw into a bone material to a pre-set force; and a patent to Daniel, et al., U.S. Pat. No. 4,712,542, that shows a device and procedure for verifying ligament isometric positioning and tensioning. Where tooling for placing and positioning of certain hip prosthesis are shown in patents to McKee, U.S. Pat. Nos. 3,801,989; Amstutz, 3,857,389; and Kaufer, et al., 3,868,730; these patents do not consider torsional testing of a seated hip femoral prosthesis.